This project intends to develo an AIDS transmission blocking vaccine based on our previous finding that maternal high affinity antibodies to the gp120 MN Primary Neutralizing Domain (PND) can protect the fetus from infection by the HIV infected mother. We will first use various gp120 MN-PND peptide-conjugates in animals to determine their immunogenicity with regard to the raising of high affinity neutralizing antibodies to MN-PND. Four immunogenic carriers will be used with the peptides to include: Tetanus toxoid, Diphtheria toxoid, PPD and BCG cell walls. In addition, human volunteers will be screened, recruited and ultimately vaccinated with MN-PND Vaccine GMP conjugates. The following groups of vollunteers will be recruited: 1. A small number of normal human volunteers to test the immunogenicity of the peptide vaccine conjugates. 2. HIV positive healthy volunteers with intact humoral immunity. 3. HIV sropositive women with the probability of becoming pregnant within 1 year of vaccination. 4. Finally, after review of te results in the above groups, a randomized controlled trial in HIV seropositive pregnant women will be designed. All vaccine trials will be coordinated with the NIH Vaccine Task Force.